This invention relates to purification of sewage based upon the activated sludge method, and particularly to an apparatus for purifying sewage, which can be easily applied and installed into an aerator vessel of existing sewage purification facilities to strikingly increase the treating capacity.
In the most sewage purification devices, generally employed oxygen is supplied to the activated sludge by blowing air into a mixture of sewage and activated sludge contained in an aeration vessel. However, since the oxygen content in the air is small, large quantity of air must be blown to supply sufficient amount of oxygen. While the air rises through the liquid in the form of bubbles, the liquid tends to be excessively agitated. Hence, with the conventional sewage purification devices, in order to obtain the treated water which is substantially free from activated sludge, it is necessary to provide a settling vessel in which the aerated liquid is allowed to stay there for a predetermined period of time, during which the activated sludge precipitates.